Styrene/tetradecyl methyl acrylate/3-methacryloxylpropyl trimethoxyl silane triblock copolymers (PSTKs), with well-defined structures and narrow molecular weight distributions, were synthesized by atom transfer radical polymerization. They were investigated as macromolecular coupling agents for the surface treatment of glass fibers. The reaction kinetics for the triblock copolymers were studied. The contact angles of the copolymers with water and diiodomethane showed that a modified-glass-fiber surface treated with a PSTK solution had strong hydrophobicity and that the impregnation of polypropylene on glass fibers was improved dramatically. In comparison with a film of 3-methacryloxylpropyl trimethoxyl silane, the polarity of the surface free energy of a PSTK film decreased, whereas the dispersion increased greatly. The critical concentration of the macromolecular coupling agents was obtained, and the monolayer saturated adsorptive capacity was calculated with the Gibbs absorption isotherm equation. (c) 2007 Wiley Periodicals, Inc.